Updraft: April 23, 2012 Archive

"Spring-tastic" start to week; Unusual "hybrid" tornadoes Saturday ?

Posted at 8:56 AM on April 23, 2012 by Paul Huttner

60s today across most of Minnesota

70s Tuesday & Wednesday

Scattered showers & T-Storms return Tuesday night & Wednesday

14 hours of daylight this week in Minnesota

2-3 minutes per day of additional daylight this week

August 20th - sun is as intense as mid-late August this week

8 tornadoes - SPC "preliminary" tornado count for Minnesota Saturday
(2 in Iowa)

Biggest "outbreak" in Minnesota since June 17, 2010?

"Hybrid" tornadoes observed Saturday?

Source: Twin Cities NWS

"Spring-tastic"

Break out the weather metaphors today. Our "spring-tacular" start to the week is brought to you by High Pressure. Now if we can just get the timing right with sun for the weekend, rain at night, everybody will be happy. Maybe in my next meteorological life.

Look for plenty of sun early Monday, but a veil of clouds may seep in this afternoon and filter our sun at times this afternoon and evening. I can't rule out a stray shower from the metro north & east tonight as an upper level wave rolls through.

Tuesday and Wednesday should bring the mildest weather in days, as temps push into the 70s south.

Source: Iowa State University

A clipper like low pressure system riding through will bring a chance at showers Tuesday night into early Wednesday. Again, it looks like the best shot at showers will be north & east of the metro, along a Duluth to Eau Claire line.

Cooler breezes late week:

Canadian high pressure will nose south Thursday into the weekend, and bring cooler temps along with. The high will battle another wave of low pressure Friday, as some attempted showers try and fight their way into southern Minnesota. If the high wins, the showers may be held south of the metro Friday. If not, expect a wet end to the week.

Right now the weekend looks mainly sunny, seasonably cool and pretty darn nice. We could see a touch of frost Saturday & Sunday morning, but that's pretty typical for the last weekend in April. Average date of last 32 degree temp at MSP? April 29th.

Source: MN Climate Working Group

Highs should stay in the upper 50s Saturday, but may mellow into the 60s Sunday.

We may actually get the timing right on weekend sun for a change!

Summer in no hurry:

Looking ahead, next week looks seasonable for the first week of May. (Can you believe it's May already next week?) A "zonal flow" may bring a couple of low pressure systems spinning through, so it looks wet and potentially stormy next week. We need the rain, so that's not all bad.

Wet pattern next week?
Source: NOAA/Climate Prediciton Center

Right now there are no signs of a big steroidal high pressure ridge, or early season heat wave ahead. That's probably a good thing, we need to ease into summer this year, and avoid deepening an already bad drought situation.

Source: NOAA/meteostar.com

Saturday Tornadoes: A rare breed of "hybrid" storm?

You may have noticed I was busy updating the blog and keeping our MPR news staff abreast of some breaking weather news for Minnesota Saturday PM. It was an unusual day to say the least. Here are some of the quirky things that happened Saturday.

-No SPC "risk area" for Minnesota

-No tornado SPC tornado watches

-One "mesoscale discussion" highlighting the potential for small tornadoes

-8 tornadoes touched down in Minnesota Saturday (SPC preliminary storm reports)

8 preliminary tornado reports in MN Saturday (2 in Iowa)
Source: NOAA/Storm Prediction Center

If the total of 8 tornadoes stands, it's the biggest number of tornadoes in a single day since the big May 17th, 2010 "super outbreak" in Minnesota that spawned a record 48 tornadoes.

Tornado sightings poured in from Clay, Wilkin, Otter Tail, Chippewa, Redwood, Swift and Douglas Counties Saturday.

Some damage was reported, and most of the tornadoes seemed to be thin "rope" or "needle" type funnels.

"Cold Air Funnel" over Cokato in July 2009
MPR listener photo with permission

"Hybrid" Funnels?

Saturday was an unusual day, synoptically speaking. A fairly strong low pressure system was dumping up to 6" of snow in the cold air over the Iron Range, and a chilly rain in the metro.

In the back side of the system, strong April sunshine generated enough heating to trigger a few "low topped" thunderstorms rising into the spinning atmosphere near the low.

It was just the right mix of spin, heating, and instability to produce some small, non-classic supercell type rotating thunderstorms...that went on to spin out several "weak" (probably EF0-EF1) tornadoes.

Saturday's twisters were what you might call "Hybrid Cold Air/Supercell Tornadoes" (my term). It's common in springtime to get so called "cold air funnels" twisting down from the sky when low pressure spins overhead, but the atmosphere is too cool to produce the classic "supercell thunderstorms."

But Saturday's storms had a little more organization on radar. They actually looked more like mini discreet, rotating supercell type storms...on a much smaller scale. The tornadoes Saturday had more "oomph" and gusto than your typical "cold air funnels."

Who knows, maybe we're entering a bizarre new weather world in Minnesota where new types of storms will form given a warming climate, and a northern latitude.

Whatever it was, I can tell you this. Saturday was one of the rarest and most interesting weather days I have ever observed in 30 years of covering Minnesota weather.

PH

SKYWARN classes teach you how to spot severe weather

Posted at 1:01 PM on April 23, 2012 by Paul Huttner (2 Comments)

So you want to be a severe weather spotter?

Here's your chance.

Metro Skywarn conducts training classes this time fo year to help train severe weather spotters to feed info to the NWS in storm situations. Here's how to get involved.

Source: Twin Cities NWS

Happy hunting!

PH

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